(Not Applicable)
(Not Applicable)
The present invention relates in general to the production of mold-cast structures, and in particular to a method for controlling the solidification rate of a molten liquid material within a mold casting chamber by measuring and regulating temperature and/or heat flow change at a plurality of chamber sites to thereby fabricate a solid structure having known characteristics produced as a result of such chosen temperature regulation.
Production of numerous products is accomplished through employment of mold fabrication technology whereby hot liquid material constituting the substance of a finished product is placed within a mold chamber shaped in the form of the desired final product and thereafter cooled to solidify and yield the finished product. Eligible materials for moldable products generally must be able to withstand heating to a flowable liquid state without untoward breakdown of components and to ultimately cool after formation into an acceptable product. Two typical families of such materials are found in plastics and metals, thereby resulting in various plastic polymers and feasibly-meltable metals being mold-formed into a myriad of products.
While the generalized steps of heating a material to melt, introducing the molten material to a mold cavity, and cooling the material to form a finished product are well known, specific procedures and methodology during these steps can significantly contribute to end product results. Thus, for example, the rate of cooling and thus solidification of particular molten metals can affect the microstructure of the finished metal structure. One prior art attempt to regulate cooling includes actual movement of a mold cavity having therein the metal through a series of decreasing temperature zones to thereby produce a general, and obviously non-precise, cooling effect over a period of time. Another prior art attempt to regulate cooling is a simple reduction of heat to the mold cavity in a non-precise manner. While solid structure formation of a molded product readily occurs through these prior art methods, the actual microstructure of the product is not standardized because consistency of cooling and therefore consistency of the solidification rate is not achieved.
In view of the vagaries experienced in the prior art, it is apparent that a need is present for a method of providing significant control over solidification rates of material formed within a mold chamber. Accordingly, a primary object of the present invention is to provide a method of controlling a solidification rate of a molten liquid material within a casting chamber of a mold by continuously monitoring and adjusting temperature values at a plurality of sites relative the casting chamber.
Another object of the present invention is to provide a method of controlling such solidification rate wherein a microprocessor determines and accordingly regulates temperature values at each such site in concordance with stored temperature measurements relating to respective extents of solidification.
Yet another object of the present invention is to provide a method of controlling such solidification rate wherein individual respective temperature controllers are provided at each respective site.
These and other objects of the present invention will become apparent throughout the description thereof which now follows.
The present invention is a method of controlling a solidification rate of a molten liquid material within a casting chamber of a mold to thereby form a solid structure fabricated of that material upon controlled cooling thereof. The method first comprises providing a stationary mold comprising a casting chamber with a heat-transferable wall having a plurality of sites each having in communication therewith a respective surface-temperature sensor for determining a respective temperature at each such site. Each site additionally includes an independently operable temperature controller for regulating each respective site temperature. The method next includes providing a microprocessor comprising a plurality of stored temperature measurements relating to respective extents of solidification of liquid material at each of the plurality of stored temperature measurements. The microprocessor is in communication with each respective surface-temperature sensor for receiving each respective temperature at each site and in communication with each respective temperature controller for selective activation and operation thereof. The casting chamber is heated to a temperature sufficient to maintain the liquid material in a molten state, and the molten liquid material is situated within the casting chamber. Finally, the microprocessor is activated for receiving each respective temperature at each site, comparing each respective temperature to the stored temperature measurements, and regulating in response thereto each respective temperature controller for continuously maintaining a rate of cooling within the casting chamber equal to chosen extents of solidification over a time period terminating upon fabrication of the solid structure.
In a second preferred embodiment, the surface-temperature sensors are replaced with or provided in conjunction with heat flux sensors for determining a respective heat removal rate at each site and the microprocessor includes a plurality of stored heat removal rates relating to respective extents of solidification of liquid material at each of these stored heat removal rates. The activated microprocessor receives each respective heat removal rate at each site, compares each heat removal rate to the stored heat removal rates, and regulates in response thereto each respective temperature controller for continuously maintaining a rate of cooling again equal to chosen extents of solidification over a time period terminating upon fabrication of the solid structure. In the second embodiment such regulation can be based only upon heat removal rates or, if provided in the microprocessor, upon a correlation of site temperatures as well as heat removal rates.
The methodology here defined permits precision temperature management in accord with historical parameters as reflected in algorithmic analyses and regulation via the microprocessor to achieve structure development in accord with specified product production.